Determination of TEMPO-oxidized cellulose nanofibril length distribution by agarose gel electrophoresis

Electron microscopy is commonly used to determine size distributions of cellulose nanofibrils (CNFs). However, the results are not always clear due to difficulty isolating individual CNFs from highly entangled networks thereof. Herein, the length distributions of TEMPO(2,2,6,6-tetramethylpiperidine-1-oxyl radical)-oxidized CNFs (T-CNFs) were determined via agarose gel electrophoresis, which is widely used for size-based separation of DNA. The high surface charge density of T-CNFs enabled effective visualization within the gel using a cationic dye, while their uniform widths facilitated length-based migration. The migration distance was inversely proportional to the fibril length. This migratory behavior was similar to that of reference DNA markers of known lengths. It was therefore possible to derive the proportions of T-CNFs of various lengths. Mapping of the mean lengths of T-CNFs that moved the same distances as did the DNA markers yielded the length relationship between the DNA markers and T-CNFs. The mass distributions of T-CNFs along the direction of motion were determined by comparing the optical densities at different locations. The new gel electrophoresis-based approach is a cost-effective and scalable alternative means by which T-CNF length can be defined, and will enable rapid quality control during industrial applications.